This invention relates to controlling of charging and discharging of a chargeable and dischargeable capacitor unit with plural electric double layer capacitors connected in series and more particularly to controlling of charging and discharging of electric double layer capacitors to be a power source used for the purpose of improving energy efficiency of vehicles including a 12V vehicle, a 42V vehicle, an electric vehicle, and a hybrid powered vehicle and a power storage such as road leveling.
As a conventional capacitor device for a vehicle, the 12V vehicle employs a lead battery while the hybrid powered vehicle employs a nickel metal hydride battery. Also, the lead battery and the nickel-cadmium battery have been used as the power storage.
A conventional power storage device including the lead storage battery, nickel-cadmium battery, and nickel metal hydride battery is a chemical cell utilizing chemical reaction. Accordingly, the conventional power storage devices are not suitable for high output because reaction speed relative to charging and discharging is extremely slow relative to electronic conduction and has shorter lifetime comparing with other electric and electronic components because reaction reversibility is apt to be degraded in connection with charging and discharging cycle.
An object of this invention is to improve a capacitor unit with plural double layer capacitors to eliminate irregularity in a state of charge of the respective double layer capacitor in the capacitor unit.
Another object of this invention is to downsize a discharging circuit for electric double layer capacitors.
More concretely, this invention has an advantage of its suitability in high output and its longer lifetime because capacitors utilizing electric double layers only absorb and desorb relative to charging and discharging the capacitor, thereby proving very fast reaction speed and maintaining its theoretical reversibility. However, a capacitor unit composed of plural electric double layer capacitors connected in series causes irregularity in the state of charge among the electric double layer capacitors and overcharging and degradation of the electric double layer capacitors. Accordingly, another object of this invention is to equalize the state of charge of plural electric double layer capacitors connected in series.
In order to resolve the above-problems, this invention provides a chargeable and dischargeable capacitor unit with plural electronic double layer capacitors connected in series is characterized in that electric double layer capacitors in a higher state of charge is subject to discharge so that a state of charging of the respective electric double layer capacitor may become approximately equal to each other.
This invention further provides the capacitor unit with plural electric double layer capacitors connected in series as above, wherein a state of charge of an electric double layer capacitor is calculated by the voltage of the electric double layer capacitor.
This invention still further provides a capacitor unit with plural electric double layer capacitors connected in series as above, wherein plural series circuits, each comprising an adjusting resistance and an electric switch, are parallelly connected relative to the respective electric double layer capacitor; and when an electric switch is turned on, an electric current running through the adjusting resistance is to be within an allowable range for the electric double layer capacitor.
This invention still further provides the capacitor unit with plural electric double layer capacitors connected in series as above, wherein an adjusting resistance being connected parallel to the respective electric double layer capacitor and adjusting a state of charge of the respective electric double layer capacitor is to be larger than a value dividing a rated voltage or a withstand voltage of the electric double layer capacitor by an upper limit current of wiring materials and parts.
This invention still further is the capacitor unit with plural electric double layer capacitors connected in series as above, wherein if a difference between a state of charging of an electric double layer capacitor in a highest state of charge and an average state of charge of the rest of electric double layer capacitors becomes an upper limit value or more, the electric double layer capacitor in the highest state of charge is subject to discharge and if the difference becomes a lower limit value or less, discharging of the electric double layer capacitor in the highest state of charge is suspended.
This invention still further is the capacitor unit with plural electric double layer capacitors connected in series as above, wherein if a difference between a state of charging of an electric double layer capacitor in a highest state of charge and a state of charging of an electric double layer capacitor in a lowest state of charge becomes an upper limit value or more, the electric double layer capacitor in the highest state of charge is subject to discharge and if the difference becomes a lower limit value or less, discharging of the electric double layer capacitor in the highest state of charge is suspended.
This invention further provides a control method of a chargeable and dischargeable capacitor unit with plural electronic double layer capacitors connected in series is characterized in that electric double layer capacitors in a higher state of charge is subject to discharge so that a state of charging of the respective electric double layer capacitor may become approximately equal to each other.
This invention still further provides a capacitor unit control apparatus, comprising a chargeable and dischargeable capacitor unit with plural electric double layer capacitors connected in series; a voltmeter measuring the voltage of the respective electric double layer capacitor; a series circuit having an adjusting resistance and an electric switch connected parallel to the respective electric double layer capacitor; and an electric switch control device turning the electric switch on to discharge the electric double layer capacitor, wherein an electric switch for an electric double layer capacitor in a higher state of charge is turned on to discharge the same so that a state of charging of the respective electric double layer capacitor may become approximately equal to each other.
This invention yet further is a chargeable and dischargeable capacitor system with plural electronic double layer capacitors connected in series, wherein an electric double layer capacitor in a higher state of charge is subject to discharge so that a state of charging of the respective electric double layer capacitor may become approximately equal to each other.
More concretely, a capacitor unit of this invention is characterized in that plural electric double layer capacitor calls or plural capacitor modules, each having 2 or more parallely connected capacitor cells, are connected in series, wherein adjusting reisistances Ri (xcexa9) and electric switches SWi are connected in parallel to the respective electric double layer capacitor Cl as shown in FIG. 1.
At that time, the adjusting resistance Ri is to be Vi/Io (xcexa9) or more if the rated voltage or the withstand voltage of the electric double layer capacitor Ci connected in parallel is Vi (V) and a current value durable for electric switch SWi connected with adjusting resistances Ri (xcexa9) in series or a copper wire is Io (A). As such, downsizing of a section positioning the adjusting resistance and the electric switch becomes possible.
In this system, regardless of the state of charge, pause, and discharge, only the electric double layer capacitor connected in parallel to the adjusting resistance is discharged by turning the electric switch of the adjusting resistance Ri on and off.